Narcolepsy is considered a neurological disorder. At its most basic level, patients with narcolepsy have a decreased ability to regulate their sleep-wake cycles. The two main symptoms of narcolepsy are excessive daytime sleepiness and abnormal rapid eye movement (REM) sleep.
Individuals with narcolepsy may feel a sudden need to take a nap and that need may be physically impossible to resist. This excessive and overwhelming daytime sleepiness is often the first symptom of narcolepsy to appear. Unfortunately, daytime sleepiness is often paired with periods of wakefulness at night. The insomnia, coupled with the excessive daytime sleepiness, can be seriously disruptive to the individual’s social, personal, and professional life.
Patients with narcolepsy may also experience cataplexy, sleep paralysis, sleep attacks, and/or hypnagogic hallucinations. Individuals who experience cataplectic episodes periodically lose muscle function and may even experience a complete body collapse. Individuals who experience sleep paralysis may have a temporary (seconds to minutes) inability to talk or move when waking. Sleep attacks cause the patient to suddenly transition from wakefulness to sleep, with no warning. Individuals who experience hypnagogic hallucinations have vivid visual, tactile, auditory, or other sensory experiences that occur when transitioning from wakefulness to sleep. In addition to those more common symptoms of narcolepsy, patients may also experience automatic behaviors whereby they continue to perform complex actions while asleep, yet, upon wakening, have no memory of performing the activities. Lastly, patients with narcolepsy, especially children, may also gain excess weight when they first develop narcolepsy.
What causes narcolepsy?
Narcolepsy affects approximately 1 in 2,000 people and there appear to be multiple causes of narcolepsy. In most cases, in fact, the exact cause of narcolepsy is unknown. Researchers have identified several genetic risk factors for narcolepsy, the most dominant of which is the human leukocyte antigen (HLA) complex. The fact that risk of narcolepsy is associated with certain HLA molecules has led scientists to propose the immune system may play a role in the development of narcolepsy. Indeed, in some people, narcolepsy appears to result from an autoimmune response to neurons in the hypothalamus of the brain that release the neuropeptide orexin. Orexin (also known as hypocretin) acts within the brain to regulate appetite and wakefulness and it is believed that disruption of orexin can cause the symptoms of narcolepsy.
Some scientists have also proposed that narcolepsy is an evolutionary throwback to the defensive mechanism of the tonic immobility reflex (playing possum).
Diagnosis of Narcolepsy
When patients have all of the symptoms of narcolepsy, then diagnosis is relatively easy. Unfortunately, however, diagnosis is not always straightforward. In general, physicians begin by giving patients a brief questionnaire known as the Epworth Sleepiness Scale (ESS). The ESS helps to determine the likelihood of the presence of a sleep disorder.
If a physician suspects that a patient has narcolepsy, then the physician typically orders a sleep study for the patient. If the patient has narcolepsy, then the sleep study results are likely to reveal that the order and length of non-REM and REM sleep periods are disturbed. In particular, individuals with narcolepsy have a tendency to go abruptly (within five minutes) from waking to REM sleep, without experiencing the typical transition through non-REM sleep. Experts believe that this disruption in sleep architecture means that the patient with narcolepsy does not experience a typical amount of deep sleep during a given night’s sleep. This results in a sleep deficit that may, at least partially, drive the excessive daytime sleepiness.
Once a diagnosis has been made, physicians typically recommend lifestyle changes as well as medications.